A control method for actively optimizing harmonics in permanent magnet synchronous motors

Abstract

The present invention discloses a control method for actively optimizing harmonics in a permanent magnet synchronous motor. The method extracts the harmonic power injected into the motor from the current and voltage of the DC bus. The DC power is first calculated based on the measured DC voltage and current. The coordinates are then transformed to the harmonic axis system to obtain the real part. The amplitude of the harmonic power is obtained through a low-pass filter. The Lagrange multiplier equation is then used to convert the constrained optimization problem into an unconstrained problem, with the minimum harmonic current amplitude as the optimization target and the harmonic power tending to zero as the constraint. The gradient descent method is used to search for the optimal harmonic current setting, which is applied to the motor through a harmonic controller to achieve minimum harmonic current injection and minimum DC power fluctuation. The method of the present invention can automatically obtain the minimum harmonic current setting to reduce DC power fluctuation, thereby reducing the pulsating torque and electromagnetic vibration of the permanent magnet synchronous motor. The method is suitable for transportation equipment that uses a permanent magnet synchronous motor as a drive device and requires low torque pulsation.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic equipment and control thereof, and particularly relates to a control method for automatically optimizing harmonic current of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in electric vehicles, marine propulsion, and other fields due to their high torque density. A typical PMSM drive system consists of a controller, inverter, current sensor, and position sensor. The controller, comprised of a fully digital control chip, collects current and position signals, generating pulse modulation signals to control the motor's current and torque. With the continuous advancement of technology and increasing demand, traditional fundamental wave control can no longer meet the requirements for low torque ripple and low vibration and noise.

[0003] The harmonic currents of permanent magnet synchronous motors (PMSMs) directly affect electromagnetic torque and vibration, generating corresponding torque ripple and electromagnetic vibration power. Currently, reducing torque ripple and electromagnetic vibration relies on offline calibration. This is a cumbersome process, requiring calibration at various operating points and requiring significant effort. When applied in practice, offline calibration results are inevitably affected by the motor's initial position, operating conditions, and variations between motors, leading to unsatisfactory results.

[0004] Therefore, it is of great significance to actively optimize and control the harmonic current in real time to reduce torque ripple and electromagnetic vibration. Summary of the Invention

[0005] In order to achieve active optimization control of harmonic current of permanent magnet synchronous motor, the present invention proposes a control method for active optimization of harmonics of permanent magnet synchronous motor, which takes DC power as input, actively optimizes harmonic current and reduces DC power fluctuation.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a control method for actively optimizing harmonics of a permanent magnet synchronous motor, which is used for a three-phase permanent magnet synchronous motor powered by an inverter, extracts the harmonic power injected into the motor from the current and voltage of a DC bus, and is based on a control system composed of control modules such as an active optimization harmonic control module, a fundamental controller, and a speed controller, wherein the active optimization harmonic control module consists of a harmonic power extraction module, a harmonic current active optimization controller, and a harmonic controller; the steps are: the harmonic power extraction module performs coordinate transformation on the DC power calculated based on the measured DC voltage and current into a harmonic axis system, takes the real part, and then filters out high-frequency fluctuations through a low-pass filter to obtain the amplitude of the harmonic power, which is used as the input of the harmonic current active optimization controller, wherein the harmonic controller of the active optimization harmonic control module generates a harmonic voltage u cdq , plus the voltage u output by the fundamental wave controller dq , and then output to the motor after coordinate transformation and pulse width modulation.

[0007] The control method for actively optimizing harmonics of a permanent magnet synchronous motor is described, and the steps implemented by the harmonic power extraction module are as follows:

[0008] The first step is to measure the DC voltage U dc and DC current I dc , multiplying the two to obtain DC power;

[0009] The second step is to perform coordinate transformation on the DC power to obtain the power fluctuation amplitude of the harmonic axis system;

[0010] The third step is to take the real part of the power fluctuation amplitude and pass the cutoff angular frequency a. h The low-pass filter removes high-frequency fluctuations and obtains the amplitude P of the hth harmonic power. dch .

[0011] The control method for actively optimizing harmonics of a permanent magnet synchronous motor is described. Its harmonic current active optimization controller converts the optimization problem into an unconstrained optimization problem based on the constraint that the harmonic power tends to zero and the optimization goal of the minimum harmonic current amplitude:

[0012]

[0013] Where c is the multiplier, d is the penalty factor, || 2 is the modulus of the vector.

[0014] The control method of the permanent magnet synchronous motor actively optimizing harmonics is described, wherein the harmonic current active optimization controller uses the harmonic current given r ±hdq The optimization goal is to minimize the amplitude of dch to zero as a constraint, and search for the harmonic current given r based on the Lagrange multiplier equation ±hdq , for this problem, the optimal solution can be obtained by using the gradient descent method. The specific search iterative steps are:

[0015] The first step is to assign initial values ​​to the parameters: harmonic current given r ±hdq k-1 and multiplier c k-1 ;

[0016] The second step is to calculate the gradient dL of the optimization problem k-1 , iteration r ±hdq k =r ±hdq k-1 +n*dL k-1 , update r ±hdq k-1 =r ±hdq k , where n is the iteration step size;

[0017] The third step is if the gradient dL k-1 If the error is less than the required value, then jump to step 4, otherwise jump back to step 2;

[0018] Step 4: Calculate dP dch k-1 With the multiplier c k =c k-1 +m*dP dch k-1 , update c k-1 =c k , where m is the multiplier iteration step size;

[0019] Step 5: If the gradient dL k-1 Less than the error requirement and dP dch k-1 If the error requirement is met, the iteration ends, otherwise jump back to the second step.

[0020] The control method of the permanent magnet synchronous motor actively optimizing harmonics is described, wherein the harmonic controller is given by the harmonic current r ±hdq and fundamental wave control error e dq Control harmonic current.

[0021] The beneficial effects of the present invention are as follows: the control method of the present invention is based on a three-phase permanent magnet synchronous motor powered by an inverter and its control system. On the basis of the fundamental wave controller of the vector control framework, an active optimization harmonic control module is added, thereby realizing active harmonic current optimization based on DC power, reducing DC power fluctuations, and achieving the purpose of low torque pulsation and low electromagnetic vibration. The method is suitable for different application scenarios using permanent magnet synchronous motors as drive devices, especially transportation equipment such as electric vehicles and electric-propelled ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A permanent magnet synchronous motor control system to which the control method of the present invention is applied;

[0023] Figure 2 Schematic diagram of the active optimization harmonic control method for a permanent magnet synchronous motor according to the present invention;

[0024] Figure 3 Schematic diagram of the structure of the harmonic power extraction module of the present invention;

[0025] Figure 4 This is a flow chart of the active optimization control method for harmonic currents of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Reference Figure 1 、 Figure 2 As shown, the present invention discloses a control method for actively optimizing harmonics in a permanent magnet synchronous motor. Within the traditional vector control framework, an active harmonic optimization control module is introduced. This module is used for a three-phase permanent magnet synchronous motor powered by an inverter, extracting the harmonic power injected into the motor from the current and voltage of the DC bus. The entire controller is a control system consisting of an active harmonic optimization control module, a fundamental wave controller, a speed controller, a coordinate transformation, and a pulse width modulation control module. The active harmonic optimization control module consists of a harmonic power extraction module, a harmonic current active optimization controller, and a harmonic controller.

[0028] The harmonic current active optimization controller can actively search for harmonic current settings, reduce DC power fluctuations, and combine the active optimization harmonic control module with vector control. The harmonic power extraction module transforms the DC power calculated based on the measured DC voltage and current into a harmonic axis system, takes the real part, and then filters out high-frequency fluctuations through a low-pass filter to obtain the amplitude of the harmonic power as the input of the harmonic current active optimization controller. The harmonic controller of the active optimization harmonic control module generates a harmonic voltage u cdq , plus the voltage u output by the fundamental wave controller dq , and then output to the motor after coordinate transformation and pulse width modulation.

[0029] Reference Figure 3 As shown in the figure, the steps to implement the harmonic power extraction module are:

[0030] The first step is to measure the DC voltage U dc and DC current I dc , and multiply the two to get the DC power.

[0031] The second step is to perform coordinate transformation on the DC power to obtain the power fluctuation amplitude (complex number) of the harmonic axis system.

[0032] The third step is to take the real part of the power fluctuation amplitude, filter out the high-frequency fluctuations through a low-pass filter, and obtain the amplitude P of the hth harmonic power. dch .

[0033] The active harmonic current optimization controller converts the optimization problem into an unconstrained optimization problem based on the constraint that the harmonic power tends to zero and the optimization goal of the minimum harmonic current amplitude:

[0034]

[0035] Where c is the multiplier, d is the penalty factor, || 2 is the modulus of the vector.

[0036] Reference Figure 4As shown in Figure 1, the harmonic current active optimization controller realizes the optimization of the given harmonic current. The optimal solution can be obtained by searching using the gradient descent method. The specific search iterative steps are:

[0037] The first step is to assign initial values ​​to the parameters: harmonic current given r ±hdq k-1 and multiplier c k-1 .

[0038] The second step is to calculate the gradient dL of the optimization problem k-1 , iteration r ±hdq k =r ±hdq k-1 +n*dL k-1 (n is the iteration step length), update r ±hdq k-1 =r ±hdq k .

[0039] The third step is if the gradient dL k-1 If the error is less than the requirement, jump to step 4, otherwise jump back to step 2.

[0040] Step 4: Calculate dP dch k-1 With the multiplier c k =c k-1 +m*dP dch k-1 (m is the multiplier iteration step), update c k-1 =c k .

[0041] Step 5: If the gradient dL k-1 Less than the error requirement and dP dch k-1 If the error requirement is met, the iteration ends, otherwise jump back to the second step.

[0042] The harmonic controller is given according to the harmonic current r ±hdq and fundamental wave control error e dq Control harmonic currents. Commonly used resonance or rotating shaft proportional-integral control methods are both effective in controlling harmonic currents, achieving active harmonic optimization. This method is used to optimize control for any harmonic of order h. Based on this, multiple active harmonic optimization control modules for different harmonics of order h can be added to achieve the same optimization effect for different harmonics.

[0043] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some embodiments of its application. A person skilled in the art may make several modifications and improvements without departing from the inventive concept of the present invention, and all of these modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A control method for actively optimizing harmonics in a permanent magnet synchronous motor, which is used for a three-phase permanent magnet synchronous motor powered by an inverter, characterized in that: The control system is composed of an active optimization harmonic control module, a fundamental wave controller and a speed controller, wherein the active optimization harmonic control module is composed of a harmonic power extraction module, a harmonic current active optimization controller and a harmonic controller; the steps are as follows: the harmonic power extraction module transforms the DC power calculated according to the measured DC voltage and current into a harmonic axis system, takes the real part and filters out high-frequency fluctuations through a low-pass filter, and the harmonic controller generates a harmonic voltage u cdq , plus the voltage output by the fundamental wave controller u dq , after coordinate transformation and pulse width modulation, it is output to the motor; the harmonic current active optimization controller converts the optimization problem into an unconstrained optimization problem according to the constraint that the harmonic power tends to zero and the optimization goal of the minimum harmonic current amplitude: , where c is the multiplier, d is the penalty factor, || 2 The modulus of the vector is: r ±hdq The optimization goal is to minimize the amplitude of P dch To zero as a constraint, the harmonic current is searched based on the Lagrange multiplier equation. r ±hdq , and use the gradient descent method to search for the optimal solution: The first step is to assign initial values ​​to the parameters: harmonic current setting r ±hdq k-1 and multipliers c k-1 ; The second step is to calculate the gradient d of the optimization problem L k-1 , iteration r ±hdq k = r ±hdq k-1 +n*d L k-1 ,renew r ±hdq k-1 = r ±hdq k , where n is the iteration step size; The third step is if the gradient d L k-1 If the error is less than the required value, then jump to step 4, otherwise jump back to step 2; Step 4: Calculate d P dch k-1 and multipliers c k = c k-1 +m*d P dch k-1 ,renew c k-1 = c k , where m is the multiplier iteration step size; Step 5: If the gradient d L k-1 Less than the error requirement and d P dch k-1 If the error requirement is met, the iteration ends, otherwise jump back to the second step.

2. A control method for actively optimizing harmonics of a permanent magnet synchronous motor according to claim 1, characterized in that: The DC voltage measured by the harmonic power extraction module U dc and DC current I dc , multiply to obtain DC power, perform coordinate transformation on DC power, obtain power fluctuation amplitude of harmonic axis system, take the real part of power fluctuation amplitude, and pass the cutoff angular frequency to obtain a h The low-pass filter removes high-frequency fluctuations and obtains h Amplitude of subharmonic power P dch .

3. The control method for actively optimizing harmonics of a permanent magnet synchronous motor according to claim 2, characterized in that: The harmonic controller is given according to the harmonic current r ±hdq and fundamental wave control error e dq Control harmonic current.

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